New interpolyelectrolyte complexes (IPECs) between oppositely charged types of Eudragit EPO and Eudragit L100 were synthesized at pH 6.0, 6.5, and 7.0 with a view to their application in oral controlled drug delivery systems. Differences among the obtained IPECs were evaluated by FTIR spectroscopy and elemental analysis. The results confirm that the polycomplexes are stabilized by intermacromolecular ionic bonds and have compositions Z = 1.02, 1.49, and 2, respectively. Monitoring of microenvironmental changes in the polycomplex matrices during swelling in model gastrointestinal fluids indicates that all IPECs can be considered as potential pH-sensitive carriers due to structural and compositional transformations. The established properties of the synthesized IPECs suggest that they have high potential to be used as pH-dependent oral drug delivery systems.